فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri - Paris Observatory

A system for wide-field astronomical imaging developed and operated
by the Institute for Astronomy at the University of Hawaii. Its
goal is to survey the sky for moving or variable objects on a continual basis,
and also produce accurate astrometry and photometry of already detected objects.
It is
situated at Haleakala Observatories near the summit of Haleakala in
Hawaii. Pan-STARRS1 (PS1) was the first part of Pan-STARRS. The
survey used a 1.8 meter telescope and a 1.4 Gigapixel camera to
image the sky in five broadband filters (g, r, i, z, y). The PS1
consortium is made up of astronomers and engineers from 14
institutions and six countries. The survey was completed in April
2014. The Pan-STARRS Project is now focusing on building PS2.

Short for Panoramic Survey Telescope and Rapid Response System.

pancake star

ستاره‌ی ِ لواشوار

setâre-ye lavâš#vaar

Fr.: étoile en crèpe

A star strongly compressed due to the → tidal force of a
→ massive black hole. The intense → gravity
of the → black hole pulls harder on the nearest part of the star,
creating an imbalance.
When the star penetrates the → tidal radius,
first it becomes cigar-shaped, then the squeezing of the tidal forces flattens the star in its
orbital plane to the shape of a → pancake.
Next the star rebounds, and as it leaves
the tidal radius, it starts to expand. A little further on its orbit the star
finally breaks up into gas fragments.
This flattening would increase the → density
and → temperature inside the star enough to
trigger intense nuclear reactions that would tear it apart
(Brassart & J.-P. Luminet, 2008, Astron. Astrophys. 481, 259).

A member of the class of stars in transition between
→ post-AGB and → white dwarf stars,
with temperatures as high as 200,000 K, mean mass about 0.6 Msun,
and log g = 5.5-8. PG 1159 stars have no
hydrogen or He I lines in their spectra, but do show weak He II lines and stronger lines of
ionized carbon and oxygen.
These stars are thought to be the exposed inner core of a star that
has exploded as a → planetary nebula and is on its way to become a
white dwarf. Also called → pre-degenerate star

Giuseppe Piazzi (1746-1826) was the first to notice the large
→ proper motion of the star, in 1804.
His observations over a period of 10 years revealed the largest proper
motion ever detected for any star at the time, leading him to baptize it
the "Flying Star;"
→ fly; → star.

PLAnetary Transits and Oscillations of stars (PLATO)

پلاتو

PLATO

Fr.: PLATO

A space observatory under development by the → European Space Agency
for launch around 2024. Its objective is to detect and characterize
→ exoplanets by means of their → transit
signature in front of a very
large sample of → bright stars,
and measure the seismic oscillations (→ asteroseismology)
of the parent stars orbited by these planets in order to understand the
properties of the exoplanetary systems.

A → binary system consisting of two
→ massive stars, which are → supergiants
of → spectral types O7.5 and O6. The two components are so
close together that they orbit each other with a period of 14.4 days only.
The Plaskett's star is a → double-line binary.
The estimated masses of the components are 43 (Plaskett A) and 51 (Plaskett B)
→ solar masses. The lower mass
component is optically brighter than the other star.
Also known as HR 2422 and HD 47129 (See, e.g., Bagnuolo et al. 1992, ApJ 385, 708).

Named after the Canadian astronomer John S. Plaskett (1865-1941), who made
a detailed spectroscopic study of this star in 1922.

A member of the first generation of stars, formed out of
pristine gas, enriched by → primordial nucleosynthesis alone.
The material from which these stars formed consisted mostly of hydrogen and helium.
Because neutral hydrogen clouds were free of dust, their cooling
mechanism was drastically ineffective.
As a result, these star forming clouds had a much higher temperature than
in the present epoch, and their → Jeans mass
was much higher. Therefore, these first generation of stars were principally
massive, with a typical mass scale of order of about 100 Msun.
Population III stars started forming about 300 million years
after the → Big Bang at → redshifts
between 50 and 6, when the Universe had between 1 and 5% of its present age.
These stars were probably responsible for the
→ reionization of the Universe. Given their high
mass, they lived only a few million years ending with either a
→ pair-instability supernova
phase or a direct collapse to a → black hole.
Population III stars thus initiated the chemical enrichment of the
Universe and opened the way to more normal modes of star formation,
namely → Population II. Some models predict a bimodal
→ initial mass function for the first stars,
allowing also for solar mass stars.
See also → extremely metal-poor star.